Milih kalimah sarta urutan patarosan dina jajal pamanggih kacida perlu, ieu bisa mangaruhan kana hasil jajal pamanggih. Thus comparisons between polls often boil down to the wording of the question. One way in which pollsters attempt to minimize this effect is to ask the same set of questions over time, in order to track changes in opinion. The most effective controls, used by attitude researchers, are:

asking enough questions to allow all aspects of an issue to be covered and to control effects due to the form of the question (such as positive or negative wording), the adequacy of the number being established quantitatively with psychometric measures such as reliability coefficients, and

analyzing the results with psychometric techniques which synthesize the answers into a few reliable scores and detect ineffective questions.

Another source of error is the deliberate or accidental use of nonrepresentative samples. For example, when home telephones were rare, telephone sampling had a built-in error because most of those surveyed were well-to-do.

People asked to participate in opinion polls also have the right to refuse; this means that the sample is self-selected and consequently a non-probability sample. The validity of the results and of the statistical techniques used to derive characteristics of the sample such as the margin of error are therefore highly questionable.